Ps4 button hijacking

I have a knockoff ps4 controller I want to link to contact points with a arduino I have 2 issues that I must resolve.

Power supply and how to read voltage from a contact point so I can activate a mod.

The plan for power is basically just link 3.3v pin into the controller battery lead but as the battery only supplys around 3.5v and arduino is made for 5v the power lights are very weak I doubt it would be stable running code under its current condition

If anyone knows a board that will run on 3.3v please let me know or a work around for a standard 5v board.

Which Arduino board are you using now?